Optimizing data storage in a dispersed storage network

ABSTRACT

A method for execution by a computing device of a dispersed storage network includes dispersed storage error encoding a data segment to produce a set of encoded data slices. Storage of more than a write threshold number of encoded data slices of the set of encoded data slices in a set of storage units is facilitated. A plurality of favorably stored encoded data slices is identified. A number of stored encoded data slices for deletion is determined, and the number of stored encoded data slices for deletion is selected from the plurality of favorably stored encoded data slices. Deletion of the selected number of stored encoded data slices for deletion is facilitated.

CROSS-REFERENCE TO RELATED APPLICATIONS

The present U.S. Utility Patent Application claims priority pursuant to 35 U.S.C. § 120 as a continuation-in-part of U.S. Utility application Ser. No. 15/818,633, entitled “UTILIZING MULTIPLE STORAGE POOLS IN A DISPERSED STORAGE NETWORK”, filed Nov. 20, 2017, which is a continuation-in-part of U.S. Utility application Ser. No. 14/984,024, entitled “REBUILDING ENCODED DATA SLICES IN A DISPERSED STORAGE NETWORK”, filed Dec. 30, 2015, issued as U.S. Pat. No. 10,078,472 on Sep. 18, 2018, which claims priority pursuant to 35 U.S.C. § 119(e) to U.S. Provisional Application No. 62/121,736, entitled “TRANSITIONING A STATE OF A DISPERSED STORAGE NETWORK”, filed Feb. 27, 2015, all of which are hereby incorporated herein by reference in their entirety and made part of the present U.S. Utility Patent Application for all purposes.

STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT

Not applicable.

INCORPORATION-BY-REFERENCE OF MATERIAL SUBMITTED ON A COMPACT DISC

Not applicable.

BACKGROUND OF THE INVENTION Technical Field of the Invention

This invention relates generally to computer networks and more particularly to dispersing error encoded data.

Description of Related Art

Computing devices are known to communicate data, process data, and/or store data. Such computing devices range from wireless smart phones, laptops, tablets, personal computers (PC), work stations, and video game devices, to data centers that support millions of web searches, stock trades, or on-line purchases every day. In general, a computing device includes a central processing unit (CPU), a memory system, user input/output interfaces, peripheral device interfaces, and an interconnecting bus structure.

As is further known, a computer may effectively extend its CPU by using “cloud computing” to perform one or more computing functions (e.g., a service, an application, an algorithm, an arithmetic logic function, etc.) on behalf of the computer. Further, for large services, applications, and/or functions, cloud computing may be performed by multiple cloud computing resources in a distributed manner to improve the response time for completion of the service, application, and/or function. For example, Hadoop is an open source software framework that supports distributed applications enabling application execution by thousands of computers.

In addition to cloud computing, a computer may use “cloud storage” as part of its memory system. As is known, cloud storage enables a user, via its computer, to store files, applications, etc. on an Internet storage system. The Internet storage system may include a RAID (redundant array of independent disks) system and/or a dispersed storage system that uses an error correction scheme to encode data for storage.

BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWING(S)

FIG. 1 is a schematic block diagram of an embodiment of a dispersed or distributed storage network (DSN) in accordance with the present invention;

FIG. 2 is a schematic block diagram of an embodiment of a computing core in accordance with the present invention;

FIG. 3 is a schematic block diagram of an example of dispersed storage error encoding of data in accordance with the present invention;

FIG. 4 is a schematic block diagram of a generic example of an error encoding function in accordance with the present invention;

FIG. 5 is a schematic block diagram of a specific example of an error encoding function in accordance with the present invention;

FIG. 6 is a schematic block diagram of an example of a slice name of an encoded data slice (EDS) in accordance with the present invention;

FIG. 7 is a schematic block diagram of an example of dispersed storage error decoding of data in accordance with the present invention;

FIG. 8 is a schematic block diagram of a generic example of an error decoding function in accordance with the present invention;

FIG. 9A is a schematic block diagram of an embodiment of a dispersed or distributed storage network (DSN) in accordance with the present invention;

FIG. 9B is a schematic block diagram of an embodiment of a dispersed or distributed storage network (DSN) in accordance with the present invention; and

FIG. 10 is a logic diagram of an example of a method of optimizing data storage in accordance with the present invention.

DETAILED DESCRIPTION OF THE INVENTION

FIG. 1 is a schematic block diagram of an embodiment of a dispersed, or distributed, storage network (DSN) 10 that includes a plurality of computing devices 12-16, a managing unit 18, an integrity processing unit 20, and a DSN memory 22. The components of the DSN 10 are coupled to a network 24, which may include one or more wireless and/or wire lined communication systems; one or more non-public intranet systems and/or public internet systems; and/or one or more local area networks (LAN) and/or wide area networks (WAN).

The DSN memory 22 includes a plurality of storage units 36 that may be located at geographically different sites (e.g., one in Chicago, one in Milwaukee, etc.), at a common site, or a combination thereof. For example, if the DSN memory 22 includes eight storage units 36, each storage unit is located at a different site. As another example, if the DSN memory 22 includes eight storage units 36, all eight storage units are located at the same site. As yet another example, if the DSN memory 22 includes eight storage units 36, a first pair of storage units are at a first common site, a second pair of storage units are at a second common site, a third pair of storage units are at a third common site, and a fourth pair of storage units are at a fourth common site. Note that a DSN memory 22 may include more or less than eight storage units 36. Further note that each storage unit 36 includes a computing core (as shown in FIG. 2, or components thereof) and a plurality of memory devices for storing dispersed error encoded data.

In various embodiments, each of the storage units operates as a distributed storage and task (DST) execution unit, and is operable to store dispersed error encoded data and/or to execute, in a distributed manner, one or more tasks on data. The tasks may be a simple function (e.g., a mathematical function, a logic function, an identify function, a find function, a search engine function, a replace function, etc.), a complex function (e.g., compression, human and/or computer language translation, text-to-voice conversion, voice-to-text conversion, etc.), multiple simple and/or complex functions, one or more algorithms, one or more applications, etc. Hereafter, a storage unit may be interchangeably referred to as a dispersed storage and task (DST) execution unit and a set of storage units may be interchangeably referred to as a set of DST execution units.

Each of the computing devices 12-16, the managing unit 18, and the integrity processing unit 20 include a computing core 26, which includes network interfaces 30-33. Computing devices 12-16 may each be a portable computing device and/or a fixed computing device. A portable computing device may be a social networking device, a gaming device, a cell phone, a smart phone, a digital assistant, a digital music player, a digital video player, a laptop computer, a handheld computer, a tablet, a video game controller, and/or any other portable device that includes a computing core. A fixed computing device may be a computer (PC), a computer server, a cable set-top box, a satellite receiver, a television set, a printer, a fax machine, home entertainment equipment, a video game console, and/or any type of home or office computing equipment. Note that each managing unit 18 and the integrity processing unit 20 may be separate computing devices, may be a common computing device, and/or may be integrated into one or more of the computing devices 12-16 and/or into one or more of the storage units 36. In various embodiments, computing devices 12-16 can include user devices and/or can be utilized by a requesting entity generating access requests, which can include requests to read or write data to storage units in the DSN.

Each interface 30, 32, and 33 includes software and hardware to support one or more communication links via the network 24 indirectly and/or directly. For example, interface 30 supports a communication link (e.g., wired, wireless, direct, via a LAN, via the network 24, etc.) between computing devices 14 and 16. As another example, interface 32 supports communication links (e.g., a wired connection, a wireless connection, a LAN connection, and/or any other type of connection to/from the network 24) between computing devices 12 & 16 and the DSN memory 22. As yet another example, interface 33 supports a communication link for each of the managing unit 18 and the integrity processing unit 20 to the network 24.

Computing devices 12 and 16 include a dispersed storage (DS) client module 34, which enables the computing device to dispersed storage error encode and decode data as subsequently described with reference to one or more of FIGS. 3-8. In this example embodiment, computing device 16 functions as a dispersed storage processing agent for computing device 14. In this role, computing device 16 dispersed storage error encodes and decodes data on behalf of computing device 14. With the use of dispersed storage error encoding and decoding, the DSN 10 is tolerant of a significant number of storage unit failures (the number of failures is based on parameters of the dispersed storage error encoding function) without loss of data and without the need for a redundant or backup copies of the data. Further, the DSN 10 stores data for an indefinite period of time without data loss and in a secure manner (e.g., the system is very resistant to unauthorized attempts at accessing the data).

In operation, the managing unit 18 performs DS management services. For example, the managing unit 18 establishes distributed data storage parameters (e.g., vault creation, distributed storage parameters, security parameters, billing information, user profile information, etc.) for computing devices 12-14 individually or as part of a group of user devices. As a specific example, the managing unit 18 coordinates creation of a vault (e.g., a virtual memory block associated with a portion of an overall namespace of the DSN) within the DSN memory 22 for a user device, a group of devices, or for public access and establishes per vault dispersed storage (DS) error encoding parameters for a vault. The managing unit 18 facilitates storage of DS error encoding parameters for each vault by updating registry information of the DSN 10, where the registry information may be stored in the DSN memory 22, a computing device 12-16, the managing unit 18, and/or the integrity processing unit 20.

The DSN managing unit 18 creates and stores user profile information (e.g., an access control list (ACL)) in local memory and/or within memory of the DSN memory 22. The user profile information includes authentication information, permissions, and/or the security parameters. The security parameters may include encryption/decryption scheme, one or more encryption keys, key generation scheme, and/or data encoding/decoding scheme.

The DSN managing unit 18 creates billing information for a particular user, a user group, a vault access, public vault access, etc. For instance, the DSN managing unit 18 tracks the number of times a user accesses a non-public vault and/or public vaults, which can be used to generate a per-access billing information. In another instance, the DSN managing unit 18 tracks the amount of data stored and/or retrieved by a user device and/or a user group, which can be used to generate a per-data-amount billing information.

As another example, the managing unit 18 performs network operations, network administration, and/or network maintenance. Network operations includes authenticating user data allocation requests (e.g., read and/or write requests), managing creation of vaults, establishing authentication credentials for user devices, adding/deleting components (e.g., user devices, storage units, and/or computing devices with a DS client module 34) to/from the DSN 10, and/or establishing authentication credentials for the storage units 36. Network administration includes monitoring devices and/or units for failures, maintaining vault information, determining device and/or unit activation status, determining device and/or unit loading, and/or determining any other system level operation that affects the performance level of the DSN 10. Network maintenance includes facilitating replacing, upgrading, repairing, and/or expanding a device and/or unit of the DSN 10.

The integrity processing unit 20 performs rebuilding of ‘bad’ or missing encoded data slices. At a high level, the integrity processing unit 20 performs rebuilding by periodically attempting to retrieve/list encoded data slices, and/or slice names of the encoded data slices, from the DSN memory 22. For retrieved encoded slices, they are checked for errors due to data corruption, outdated version, etc. If a slice includes an error, it is flagged as a ‘bad’ slice. For encoded data slices that were not received and/or not listed, they are flagged as missing slices. Bad and/or missing slices are subsequently rebuilt using other retrieved encoded data slices that are deemed to be good slices to produce rebuilt slices. The rebuilt slices are stored in the DSN memory 22.

FIG. 2 is a schematic block diagram of an embodiment of a computing core 26 that includes a processing module 50, a memory controller 52, main memory 54, a video graphics processing unit 55, an input/output (IO) controller 56, a peripheral component interconnect (PCI) interface 58, an IO interface module 60, at least one IO device interface module 62, a read only memory (ROM) basic input output system (BIOS) 64, and one or more memory interface modules. The one or more memory interface module(s) includes one or more of a universal serial bus (USB) interface module 66, a host bus adapter (HBA) interface module 68, a network interface module 70, a flash interface module 72, a hard drive interface module 74, and a DSN interface module 76.

The DSN interface module 76 functions to mimic a conventional operating system (OS) file system interface (e.g., network file system (NFS), flash file system (FFS), disk file system (DFS), file transfer protocol (FTP), web-based distributed authoring and versioning (WebDAV), etc.) and/or a block memory interface (e.g., small computer system interface (SCSI), internet small computer system interface (iSCSI), etc.). The DSN interface module 76 and/or the network interface module 70 may function as one or more of the interface 30-33 of FIG. 1. Note that the IO device interface module 62 and/or the memory interface modules 66-76 may be collectively or individually referred to as IO ports.

FIG. 3 is a schematic block diagram of an example of dispersed storage error encoding of data. When a computing device 12 or 16 has data to store it disperse storage error encodes the data in accordance with a dispersed storage error encoding process based on dispersed storage error encoding parameters. Here, the computing device stores data object 40, which can include a file (e.g., text, video, audio, etc.), or other data arrangement. The dispersed storage error encoding parameters include an encoding function (e.g., information dispersal algorithm (IDA), Reed-Solomon, Cauchy Reed-Solomon, systematic encoding, non-systematic encoding, on-line codes, etc.), a data segmenting protocol (e.g., data segment size, fixed, variable, etc.), and per data segment encoding values. The per data segment encoding values include a total, or pillar width, number (T) of encoded data slices per encoding of a data segment i.e., in a set of encoded data slices); a decode threshold number (D) of encoded data slices of a set of encoded data slices that are needed to recover the data segment; a read threshold number (R) of encoded data slices to indicate a number of encoded data slices per set to be read from storage for decoding of the data segment; and/or a write threshold number (W) to indicate a number of encoded data slices per set that must be accurately stored before the encoded data segment is deemed to have been properly stored. The dispersed storage error encoding parameters may further include slicing information (e.g., the number of encoded data slices that will be created for each data segment) and/or slice security information (e.g., per encoded data slice encryption, compression, integrity checksum, etc.).

In the present example, Cauchy Reed-Solomon has been selected as the encoding function (a generic example is shown in FIG. 4 and a specific example is shown in FIG. 5); the data segmenting protocol is to divide the data object into fixed sized data segments; and the per data segment encoding values include: a pillar width of 5, a decode threshold of 3, a read threshold of 4, and a write threshold of 4. In accordance with the data segmenting protocol, the computing device 12 or 16 divides data object 40 into a plurality of fixed sized data segments (e.g., 1 through Y of a fixed size in range of Kilo-bytes to Tera-bytes or more). The number of data segments created is dependent of the size of the data and the data segmenting protocol.

The computing device 12 or 16 then disperse storage error encodes a data segment using the selected encoding function (e.g., Cauchy Reed-Solomon) to produce a set of encoded data slices. FIG. 4 illustrates a generic Cauchy Reed-Solomon encoding function, which includes an encoding matrix (EM), a data matrix (DM), and a coded matrix (CM). The size of the encoding matrix (EM) is dependent on the pillar width number (T) and the decode threshold number (D) of selected per data segment encoding values. To produce the data matrix (DM), the data segment is divided into a plurality of data blocks and the data blocks are arranged into D number of rows with Z data blocks per row. Note that Z is a function of the number of data blocks created from the data segment and the decode threshold number (D). The coded matrix is produced by matrix multiplying the data matrix by the encoding matrix.

FIG. 5 illustrates a specific example of Cauchy Reed-Solomon encoding with a pillar number (T) of five and decode threshold number of three. In this example, a first data segment is divided into twelve data blocks (D1-D12). The coded matrix includes five rows of coded data blocks, where the first row of X11-X14 corresponds to a first encoded data slice (EDS 1_1), the second row of X21-X24 corresponds to a second encoded data slice (EDS 2_1), the third row of X31-X34 corresponds to a third encoded data slice (EDS 3_1), the fourth row of X41-X44 corresponds to a fourth encoded data slice (EDS 4_1), and the fifth row of X51-X54 corresponds to a fifth encoded data slice (EDS 5_1). Note that the second number of the EDS designation corresponds to the data segment number.

Returning to the discussion of FIG. 3, the computing device also creates a slice name (SN) for each encoded data slice (EDS) in the set of encoded data slices. A typical format for a slice name 80 is shown in FIG. 6. As shown, the slice name (SN) 80 includes a pillar number of the encoded data slice (e.g., one of 1-T), a data segment number (e.g., one of 1-Y), a vault identifier (ID), a data object identifier (ID), and may further include revision level information of the encoded data slices. The slice name functions as, at least part of, a DSN address for the encoded data slice for storage and retrieval from the DSN memory 22.

As a result of encoding, the computing device 12 or 16 produces a plurality of sets of encoded data slices, which are provided with their respective slice names to the storage units for storage. As shown, the first set of encoded data slices includes EDS 1_1 through EDS 5_1 and the first set of slice names includes SN 1_1 through SN 5_1 and the last set of encoded data slices includes EDS 1_Y through EDS 5_Y and the last set of slice names includes SN 1_Y through SN 5_Y.

FIG. 7 is a schematic block diagram of an example of dispersed storage error decoding of a data object that was dispersed storage error encoded and stored in the example of FIG. 4. In this example, the computing device 12 or 16 retrieves from the storage units at least the decode threshold number of encoded data slices per data segment. As a specific example, the computing device retrieves a read threshold number of encoded data slices.

To recover a data segment from a decode threshold number of encoded data slices, the computing device uses a decoding function as shown in FIG. 8. As shown, the decoding function is essentially an inverse of the encoding function of FIG. 4. The coded matrix includes a decode threshold number of rows (e.g., three in this example) and the decoding matrix in an inversion of the encoding matrix that includes the corresponding rows of the coded matrix. For example, if the coded matrix includes rows 1, 2, and 4, the encoding matrix is reduced to rows 1, 2, and 4, and then inverted to produce the decoding matrix.

FIGS. 9A and 9B are schematic block diagrams of another embodiment of a dispersed storage network (DSN) that includes the computing device 16 of FIG. 1 and a storage pool 570. The computing device 16 includes the DS client module 34 of FIG. 1. The storage pool includes a set of DST execution (EX) units. Each DST execution unit may be implemented utilizing the storage unit 36 of FIG. 1. The storage pool may include a number of DST execution units in accordance with an information dispersal algorithm (IDA) width number when data is encoded using a dispersed storage error coding function to produce one or more sets of encoded data slices for storage in the set of DST execution units, where a decode threshold number of encoded data slices of each set of encoded data slices is required to recover the data. For example, the set of DST execution units includes DST execution units 1-16 and 10 encoded data slices are required from each set for data recovery when the IDA width is 16 and the decode threshold is 10. The DSN functions to optimize the data storage.

The DSN can optimize data storage by utilizing Trimmed Writes, which is a scheme to augment write availability and worst-case reliability without sacrificing expansion factor. In some typical dispersal configurations, consisting of an IDA Threshold, a Write Threshold, and a Width, the difference between IDA Threshold and Write Threshold can determine data reliability, while the difference between Write Threshold and Width can determine write availability. However, since all slices are stored (including those beyond Write Threshold) storage efficiency will be lower than it could otherwise be. To overcome this, the feature of “Trimmed Writes” can be used.

A computing device can implement Trimmed Writes when it determines to “undo” the extra slices (those written beyond Write Threshold) after the source is successfully written to at least a write threshold number of locations. For example, in a 10-of-20 with a Write Threshold of 15, the computing device can attempt to write at least 15 slices (and up to 20). After successfully writing some number of slices between 15 and 20, the number of excess slices can be selected to be “undone”. For example, if 18 slices were written successfully, then 3 slices (Number written successfully—Write Threshold) can be selected to be undone. The computing device will then issue Undo Requests to 3 storage units for the newly written slice to bring it down to Write Threshold. This lowers the expansion factor from Width/IDA Threshold, to Write Threshold/IDA Threshold, and meanwhile preserves the worst-case reliability, and write availability of the former system. Since the worst-case reliability (rather than reliability when all slices are written) can be the most important determinate factor in assessing system reliability, such systems are not much less reliable in practice, and can be more reliable, as it allows possible larger differences between IDA Threshold and Write Threshold (which otherwise would not be done due to decreased write availability and/or increased expansion factor). This feature can be used in conjunction with deferred rebuilding (and limited rebuilding) such that when rebuilding the sources, a rebuilder module of the DSN will not attempt to rebuild sources having at least a write threshold number of slices, and upon rebuilding, not storing more than a write-threshold number of slices.

FIG. 9A illustrates steps of an example of operation of the optimizing of the data storage where the DS client module 34 dispersed storage error encodes a data segment of the data to produce a set of encoded data slices (e.g., encoded data slices 1-16). Having produced the set of encoded data slices, the DS client module 34 can facilitate storage of greater than a write threshold number of encoded data slices of the set of encoded data slices, where the write threshold number is greater than the decode threshold number and less than the IDA width number. For example, the write threshold may be 13 when the IDA width is 16 and the decode threshold is 10. The data retrieval reliability is a function of a difference between the write threshold and the decode threshold and write availability is a function of a difference between the IDA width and the write threshold.

The facilitating of the storage of the greater than a write threshold number of encoded data slices can include generating a set of write slice requests 572 that includes the set of encoded data slices, sending (e.g., via the network 24 of FIG. 1) the set of write slice requests 572 to the set of DST execution units 1-16, receiving write slice responses 574 from at least some of the DST execution units, identifying a number of favorably stored encoded data slices of the set of encoded data slices based on the received write slice responses 574, and/or sending another write slice request 572 when the number of favorably stored encoded data slices is less than or equal to the write threshold. For example, the DS client module 34 facilitates storage of all 16 encoded data slices except for encoded data slice 15 when a storage error occurs for encoded data slice 15 and the write threshold is 13.

FIG. 9B illustrates further steps of the example of operation of the optimizing of the data storage where the DS client module 34 determines a number of stored encoded data slices for deletion. The determining can include calculating a difference between the number of favorably stored encoded data slices and a write threshold number. For example, the DS client module 34 determines to delete to encoded data slices when the number of favorable encoded data slices is 15 and the write threshold is 13.

Having determined the number of stored encoded data slices for deletion, the DS client module 34 can select the number of stored encoded data slices for deletion from the favorably stored encoded data slices. The selecting can be based on one or more of performing a random selection, a predetermination, and/or selecting error coded slices when the unity matrix is utilized in an encoding matrix of the dispersed storage error coding function (e.g., encoded data slices 11-16 as candidates of error coded slices). For example, the DS client module 34 selects encoded data slices 14 and 16 for deletion when encoded data slices 11-16 are error coded slices.

Having selected the stored encoded data slices for deletion, the DS client module 34 can facilitate deletion of the selected number of stored encoded data slices for deletion. The facilitating of the deletion can include the DS client module 34 issuing delete slice requests 576 (e.g., delete slice, a rollback request, an undo request) to DST execution units associated with the selected number of stored encoded data slices for deletion, receiving delete slice responses 578, and/or retrying sending of a particular delete slice request 576 when not receiving an indication of favorable deletion of an encoded data slice within a deletion time frame.

Having successfully deleted the selected encoded data slices for deletion, the DST client module 34 has completed a trimming process to maintain the number of stored encoded data slices of the set of encoded data slices at the write threshold number. The DS client module 34 can further indicate that the rebuilding of encoded data slices of the set of encoded data slices beyond the successfully stored and maintained write threshold number is unnecessary. For example, a rebuilding process rebuilds encoded data slice 9 when encoded data slice 9 is associated with a storage error, but does not rebuild encoded data slices 14, 15, and 16 when the DST client module 34 has indicated that the rebuilding of encoded data slices of the set of encoded data slices beyond the successfully stored and maintained write threshold number is unnecessary.

In various embodiments, a processing system of a computing device includes at least one processor and a memory that stores operational instructions, that when executed by the at least one processor cause the processing system to dispersed storage error encode a data segment to produce a set of encoded data slices. Storage of more than a write threshold number of encoded data slices of the set of encoded data slices in a set of storage units is facilitated. A plurality of favorably stored encoded data slices is identified. A number of stored encoded data slices for deletion is determined, and the number of stored encoded data slices for deletion is selected from the plurality of favorably stored encoded data slices. Deletion of the selected number of stored encoded data slices for deletion is facilitated. As used herein, “deleting” a slice includes erasing, removing from memory, undoing the slice, rolling back the slice or other methods of reversing the write of the slice. Consider a transaction system for example. Instead of sending a “commit” message following a write request, a “rollback” can be performed. These actions amount to a deletion since the commitment of the slice is abandoned.

In various embodiments, facilitating the storage of the more than a write threshold number of encoded data slices includes generating a plurality of write slice requests that includes the more than a write threshold number of encoded data slices, and further includes sending the plurality of write slice requests to the set of storage units. In various embodiments, identifying the plurality of favorably stored encoded data slices includes receiving a plurality of write slice responses from the set of storage units and interpreting the plurality write slice responses to determine the plurality of favorably stored encoded data slices. In various embodiments, determining the number of stored encoded data slices for deletion includes calculating a difference between a number of the plurality of favorably stored encoded data slices and the write threshold number, where the number of stored encoded data slices for deletion is equal to the difference.

In various embodiments, selecting the number of stored encoded data slices for deletion includes utilizing a selection scheme that is selected from a plurality of selection scheme options. In various embodiments, the plurality of favorably stored encoded data slices includes a first subset of strictly-data encoded data slices and a second subset of not-strictly-data encoded data slices. The first subset and the second subset are non-null, mutually exclusive, and collectively exhaustive with respect to the plurality of favorably stored encoded data slices. The number of stored encoded data slices for deletion are selected from the second subset of encoded data slices. In various embodiments, the second subset of encoded data slices is identified by the computing device.

In various embodiments, the plurality of favorably stored encoded data slices includes a first subset of encoded data slices stored in a favorably performing subset of the set of storage units, and further includes a second subset of encoded data slices stored in an unfavorably performing subset of the set of storage units. The first subset and the second subset are non-null, mutually exclusive, and collectively exhaustive with respect to the plurality of favorably stored encoded data slices. The number of stored encoded data slices for deletion are selected from the second subset. In various embodiments, the unfavorably performing subset of the set of storage units is identified by the computing device, and the second subset of encoded data slices is identified by the computing device based on the unfavorably performing subset.

In various embodiments, facilitating the deletion of the selected number of stored encoded data slices includes identifying a subset of storage units of the set of storage units associated with the selected number of stored encoded data slices for deletion. Delete requests are issued to the subset of storage units to delete the selected number of stored encoded data slices for deletion. The delete requests include a slice name and a revision level. Delete responses are received from the subset of storage units. A retry deletion sequence is performed when a favorable number of delete responses are not received within a response timeframe.

FIG. 10 is a flowchart illustrating an example of optimizing data storage. In particular, a method is presented for use in association with one or more functions and features described in conjunction with FIGS. 1-9B, for execution by a computing device that includes a processor or via another processing system of a dispersed storage network that includes at least one processor and memory that stores instruction that configure the processor or processors to perform the steps described below.

The method includes step 584 where a processing system (e.g., of a distributed storage and task (DS) client module and/or of a computing device) dispersed storage error encodes a data segment to produce a set of encoded data slices in accordance with an IDA width and a decode threshold number. The method continues at step 586 where the processing system facilitates storage of more than a write threshold number of encoded data slices of the set of encoded data slices in a set of storage units. For example, the processing system generates more than a write threshold number of write slice requests that includes encoded data slices of the set of encoded data slices and sends the write slice requests to the set of storage units to facilitate at least a storage of greater than a write threshold number of encoded data slices.

The method continues at step 588 where the processing system identifies a plurality of favorably stored encoded data slices. For example, the processing system receives write slice responses and interprets the write slice responses to produce the number of favorably stored encoded data slices. The method continues at step 590 where the processing system determines a number of stored encoded data slices for deletion. For example, the processing system calculates a difference between the number of favorably stored encoded data slices and the write threshold number as the number for deletion.

The method continues at step 592 where the processing system selects the number of stored encoded data slices for deletion from the favorably stored encoded data slices. The processing system can perform the selection based on a selection scheme. The processing system can choose the selection scheme based on at least one of a predetermined pattern, interpreting system registry information, and/or receiving instructions. The selection schemes can include choosing error coded slices identified as being associated with not strictly data and/or not choosing error coded slices that are identified as being associated with strictly data; performing a random selection; and/or selecting slices associated with identified porous, insecure, or otherwise unfavorably performing storage units and/or not selecting slices associated with identified non-porous, secure, or otherwise favorably performing storage units.

The method continues at step 594 where the processing system facilitates deletion of the selected number of stored encoded data slices for deletion. For example, the processing system identifies storage units associated with the selected number of stored encoded data slices for deletion (e.g., performs a lookup in a slice location table), issues delete requests to the identified storage units to delete the selected number of stored encoded data slices for deletion (e.g., where the delete request includes one or more of slice names and revision levels), receives delete responses, and/or performs a retry deletion sequence when not receiving a favorable number of delete responses within a response timeframe.

In various embodiments, a non-transitory computer readable storage medium includes at least one memory section that stores operational instructions that, when executed by a processing system of a dispersed storage network (DSN) that includes a processor and a memory, causes the processing system to dispersed storage error encode a data segment to produce a set of encoded data slices. Storage of more than a write threshold number of encoded data slices of the set of encoded data slices in a set of storage units is facilitated. A plurality of favorably stored encoded data slices is identified. A number of stored encoded data slices for deletion is determined, and the number of stored encoded data slices for deletion is selected from the plurality of favorably stored encoded data slices. Deletion of the selected number of stored encoded data slices for deletion is facilitated.

It is noted that terminologies as may be used herein such as bit stream, stream, signal sequence, etc. (or their equivalents) have been used interchangeably to describe digital information whose content corresponds to any of a number of desired types (e.g., data, video, speech, audio, etc. any of which may generally be referred to as ‘data’).

As may be used herein, the terms “substantially” and “approximately” provides an industry-accepted tolerance for its corresponding term and/or relativity between items. Such an industry-accepted tolerance ranges from less than one percent to fifty percent and corresponds to, but is not limited to, component values, integrated circuit process variations, temperature variations, rise and fall times, and/or thermal noise. Such relativity between items ranges from a difference of a few percent to magnitude differences. As may also be used herein, the term(s) “configured to”, “operably coupled to”, “coupled to”, and/or “coupling” includes direct coupling between items and/or indirect coupling between items via an intervening item (e.g., an item includes, but is not limited to, a component, an element, a circuit, and/or a module) where, for an example of indirect coupling, the intervening item does not modify the information of a signal but may adjust its current level, voltage level, and/or power level. As may further be used herein, inferred coupling (i.e., where one element is coupled to another element by inference) includes direct and indirect coupling between two items in the same manner as “coupled to”. As may even further be used herein, the term “configured to”, “operable to”, “coupled to”, or “operably coupled to” indicates that an item includes one or more of power connections, input(s), output(s), etc., to perform, when activated, one or more its corresponding functions and may further include inferred coupling to one or more other items. As may still further be used herein, the term “associated with”, includes direct and/or indirect coupling of separate items and/or one item being embedded within another item.

As may be used herein, the term “compares favorably”, indicates that a comparison between two or more items, signals, etc., provides a desired relationship. For example, when the desired relationship is that signal 1 has a greater magnitude than signal 2, a favorable comparison may be achieved when the magnitude of signal 1 is greater than that of signal 2 or when the magnitude of signal 2 is less than that of signal 1. As may be used herein, the term “compares unfavorably”, indicates that a comparison between two or more items, signals, etc., fails to provide the desired relationship.

As may also be used herein, the terms “processing system”, “processing module”, “processing circuit”, “processor”, and/or “processing unit” may be used interchangeably, and may be a single processing device or a plurality of processing devices. Such a processing device may be a microprocessor, micro-controller, digital signal processor, microcomputer, central processing unit, field programmable gate array, programmable logic device, state machine, logic circuitry, analog circuitry, digital circuitry, and/or any device that manipulates signals (analog and/or digital) based on hard coding of the circuitry and/or operational instructions. The processing system, processing module, module, processing circuit, and/or processing unit may be, or further include, memory and/or an integrated memory element, which may be a single memory device, a plurality of memory devices, and/or embedded circuitry of another processing system, processing module, module, processing circuit, and/or processing unit. Such a memory device may be a read-only memory, random access memory, volatile memory, non-volatile memory, static memory, dynamic memory, flash memory, cache memory, and/or any device that stores digital information. Note that if the processing system, processing module, module, processing circuit, and/or processing unit includes more than one processing device, the processing devices may be centrally located (e.g., directly coupled together via a wired and/or wireless bus structure) or may be distributedly located (e.g., cloud computing via indirect coupling via a local area network and/or a wide area network). Further note that if the processing system, processing module, module, processing circuit, and/or processing unit implements one or more of its functions via a state machine, analog circuitry, digital circuitry, and/or logic circuitry, the memory and/or memory element storing the corresponding operational instructions may be embedded within, or external to, the circuitry comprising the state machine, analog circuitry, digital circuitry, and/or logic circuitry. Still further note that, the memory element may store, and the processing system, processing module, module, processing circuit, and/or processing unit executes, hard coded and/or operational instructions corresponding to at least some of the steps and/or functions illustrated in one or more of the Figures. Such a memory device or memory element can be included in an article of manufacture.

One or more embodiments have been described above with the aid of method steps illustrating the performance of specified functions and relationships thereof. The boundaries and sequence of these functional building blocks and method steps have been arbitrarily defined herein for convenience of description. Alternate boundaries and sequences can be defined so long as the specified functions and relationships are appropriately performed. Any such alternate boundaries or sequences are thus within the scope and spirit of the claims. Further, the boundaries of these functional building blocks have been arbitrarily defined for convenience of description. Alternate boundaries could be defined as long as the certain significant functions are appropriately performed. Similarly, flow diagram blocks may also have been arbitrarily defined herein to illustrate certain significant functionality.

To the extent used, the flow diagram block boundaries and sequence could have been defined otherwise and still perform the certain significant functionality. Such alternate definitions of both functional building blocks and flow diagram blocks and sequences are thus within the scope and spirit of the claims. One of average skill in the art will also recognize that the functional building blocks, and other illustrative blocks, modules and components herein, can be implemented as illustrated or by discrete components, application specific integrated circuits, processors executing appropriate software and the like or any combination thereof.

In addition, a flow diagram may include a “start” and/or “continue” indication. The “start” and “continue” indications reflect that the steps presented can optionally be incorporated in or otherwise used in conjunction with other routines. In this context, “start” indicates the beginning of the first step presented and may be preceded by other activities not specifically shown. Further, the “continue” indication reflects that the steps presented may be performed multiple times and/or may be succeeded by other activities not specifically shown. Further, while a flow diagram indicates a particular ordering of steps, other orderings are likewise possible provided that the principles of causality are maintained.

The one or more embodiments are used herein to illustrate one or more aspects, one or more features, one or more concepts, and/or one or more examples. A physical embodiment of an apparatus, an article of manufacture, a machine, and/or of a process may include one or more of the aspects, features, concepts, examples, etc. described with reference to one or more of the embodiments discussed herein. Further, from figure to figure, the embodiments may incorporate the same or similarly named functions, steps, modules, etc. that may use the same or different reference numbers and, as such, the functions, steps, modules, etc. may be the same or similar functions, steps, modules, etc. or different ones.

Unless specifically stated to the contra, signals to, from, and/or between elements in a figure of any of the figures presented herein may be analog or digital, continuous time or discrete time, and single-ended or differential. For instance, if a signal path is shown as a single-ended path, it also represents a differential signal path. Similarly, if a signal path is shown as a differential path, it also represents a single-ended signal path. While one or more particular architectures are described herein, other architectures can likewise be implemented that use one or more data buses not expressly shown, direct connectivity between elements, and/or indirect coupling between other elements as recognized by one of average skill in the art.

The term “module” is used in the description of one or more of the embodiments. A module implements one or more functions via a device such as a processor or other processing device or other hardware that may include or operate in association with a memory that stores operational instructions. A module may operate independently and/or in conjunction with software and/or firmware. As also used herein, a module may contain one or more sub-modules, each of which may be one or more modules.

As may further be used herein, a computer readable memory includes one or more memory elements. A memory element may be a separate memory device, multiple memory devices, or a set of memory locations within a memory device. Such a memory device may be a read-only memory, random access memory, volatile memory, non-volatile memory, static memory, dynamic memory, flash memory, cache memory, and/or any device that stores digital information. The memory device may be in a form a solid state memory, a hard drive memory, cloud memory, thumb drive, server memory, computing device memory, and/or other physical medium for storing digital information.

While particular combinations of various functions and features of the one or more embodiments have been expressly described herein, other combinations of these features and functions are likewise possible. The present disclosure is not limited by the particular examples disclosed herein and expressly incorporates these other combinations. 

What is claimed is:
 1. A method for execution by a computing device that includes a processor, the method comprises: dispersed storage error encoding a data segment to produce a set of encoded data slices that includes more than a write threshold number of encoded data slices; facilitating storage of a proper subset of the set of encoded data slices in a set of storage units; and facilitating deletion of a number of encoded data slices from the set of storage units, wherein the number of encoded data slices are included in the proper subset of the set of encoded data slices, and wherein the number of encoded data slices is equal to a difference between a number of encoded data slices in the proper subset and the write threshold number.
 2. The method of claim 1, wherein facilitating the storage of the proper subset of the set of encoded data slices includes: generating a plurality of write slice requests that includes the proper subset of the set of encoded data slices; and sending the plurality of write slice requests to the set of storage units.
 3. The method of claim 1, further comprising: receiving a plurality of write slice responses from the set of storage units; and interpreting the plurality write slice responses to determine the proper subset of the set of encoded data slices are favorably stored, wherein a storage error occurred for at least one encoded data slice in a set difference between the set of encoded data slices and the proper subset of the set of encoded data slices.
 4. The method of claim 1, further comprising: determining the number of encoded data slices for deletion by calculating the difference between the number of encoded data slices in the proper subset and the write threshold number.
 5. The method of claim 1, further comprising: selecting a selection scheme from a plurality of selection scheme options; and selecting the number of encoded data slices for deletion by utilizing a selection scheme.
 6. The method of claim 1, wherein the proper subset of the set of encoded data slices includes a first subset of strictly-data encoded data slices and a second subset of not-strictly-data encoded data slices, wherein the first subset and the second subset are non-null, mutually exclusive, and collectively exhaustive with respect to the proper subset of the set of encoded data slices, and wherein the number of encoded data slices are selected from the second subset of not-strictly-data encoded data slices.
 7. The method of claim 6, further comprising identifying the second subset of not-strictly-data encoded data slices.
 8. The method of claim 1, wherein the proper subset of the set of encoded data slices includes a first subset of encoded data slices stored in a favorably performing subset of the set of storage units, wherein the proper subset of the set of encoded data slices further includes a second subset of encoded data slices stored in an unfavorably performing subset of the set of storage units, wherein the first subset and the second subset are non-null, mutually exclusive, and collectively exhaustive with respect to the proper subset of the set of encoded data slices, and wherein the number of encoded data slices for are selected from the second subset.
 9. The method of claim 8, further comprising: identifying the unfavorably performing subset of the set of storage units; and identifying the second subset of encoded data slices based on the unfavorably performing sub set.
 10. The method of claim 1, wherein facilitating the deletion of the number of encoded data slices from the set of storage units includes: identifying a subset of storage units of the set of storage units associated with the number of encoded data slices; issuing delete requests to the subset of storage units to delete the number of encoded data slices, wherein the delete requests include a slice name and a revision level; receiving delete responses from the subset of storage units; and performing a retry deletion sequence when a favorable number of delete responses are not received within a response timeframe.
 11. A processing system of a computing device comprises: at least one processor; a memory that stores operational instructions, that when executed by the at least one processor cause the processing system to: dispersed storage error encode a data segment to produce a set of encoded data slices that includes more than a write threshold number of encoded data slices; facilitate storage of a proper subset of the set of encoded data slices in a set of storage units; and facilitate deletion of a number of encoded data slices from the set of storage units, wherein the number of encoded data slices are included in the proper subset of the set of encoded data slices, and wherein the number of encoded data slices is equal to a difference between a number of encoded data slices in the proper subset and the write threshold number.
 12. The processing system of claim 11, wherein facilitating the storage of the proper subset of the set of encoded data slices includes: generating a plurality of write slice requests that includes the proper subset of the set of encoded data slices; and sending the plurality of write slice requests to the set of storage units.
 13. The processing system of claim 11, wherein the operational instructions, when executed by the at least one processor, further cause the processing system to: receive a plurality of write slice responses from the set of storage units; and interpret the plurality write slice responses to determine the proper subset of the set of encoded data slices are favorably stored, wherein a storage error occurred for at least one encoded data slice in a set difference between the set of encoded data slices and the proper subset of the set of encoded data slices.
 14. The processing system of claim 11, wherein the operational instructions, when executed by the at least one processor, further cause the processing system to: determine the number of encoded data slices for deletion by calculating the difference between the number of encoded data slices in the proper subset and the write threshold number.
 15. The processing system of claim 11, wherein the operational instructions, when executed by the at least one processor, further cause the processing system to: select a selection scheme from a plurality of selection scheme options; and select the number of encoded data slices for deletion by utilizing a selection scheme.
 16. The processing system of claim 11, wherein the proper subset of the set of encoded data slices includes a first subset of strictly-data encoded data slices and a second subset of not-strictly-data encoded data slices, wherein the first subset and the second subset are non-null, mutually exclusive, and collectively exhaustive with respect to the proper subset of the set of encoded data slices, and wherein the number of encoded data slices are selected from the second subset of not-strictly-data encoded data slices.
 17. The processing system of claim 11, wherein the proper subset of the set of encoded data slices includes a first subset of encoded data slices stored in a favorably performing subset of the set of storage units, wherein the proper subset of the set of encoded data slices further includes a second subset of encoded data slices stored in an unfavorably performing subset of the set of storage units, wherein the first subset and the second subset are non-null, mutually exclusive, and collectively exhaustive with respect to the proper subset of the set of encoded data slices, and wherein the number of encoded data slices are selected from the second subset.
 18. The processing system of claim 17, wherein the operational instructions, when executed by the at least one processor, further cause the processing system to: identify the unfavorably performing subset of the set of storage units; and identify the second subset of encoded data slices based on the unfavorably performing sub set.
 19. The processing system of claim 11, wherein facilitating the deletion of the number of encoded data slices from the set of storage units includes: identifying a subset of storage units of the set of storage units associated with the number of encoded data slices; issuing delete requests to the subset of storage units to delete the number of encoded data slices, wherein the delete requests include a slice name and a revision level; receiving delete responses from the subset of storage units; and performing a retry deletion sequence when a favorable number of delete responses are not received within a response timeframe.
 20. A non-transitory computer readable storage medium comprises: at least one memory section that stores operational instructions that, when executed by a processing system of a dispersed storage network (DSN) that includes a processor and a memory, causes the processing system to: dispersed storage error encode a data segment to produce a set of encoded data slices that includes more than a write threshold number of encoded data slices; facilitate storage of a proper subset of the set of encoded data slices in a set of storage units; and facilitate deletion of a number of encoded data slices from the set of storage units, wherein the number of encoded data slices are included in the proper subset of the set of encoded data slices, and wherein the number of encoded data slices is equal to a difference between a number of encoded data slices in the proper subset and the write threshold number. 